Determination of Net Radiation Balance using Satellite Imagery in Odeda Local Government Area, Ogun State, Nigeria

Abstract

The energy received on the earth surface is responsible for driving activities on the earth and not all energy emitted by the sun reaches the earth surface; some are absorbed, reflected or scattered. There is need to determine the amount of energy that reaches the earth surface since not all the energy emitted from the sun reaches the earth. This energy is also responsible for making our general climate warm which ultimately brings us to the determination of Net radiation. This study applied remote sensing method to determine net radiation over Odeda Local Government Area. A Sentinel image from 2013 covering the study area was downloaded and computations were done using bands 5 and 7. These bands were used to compute the surface albedo, incoming short wave radiation, incoming long wave radiation and outgoing long wave radiation. The spectral signatures for each component from sentinel data were analysed, using the ArcGIS 10.6. The results showed the net radiation to be of moderate intensity with values ranging between 630.83 wm-2 and 684.68 wm^-2 . The mean value over majority of the area was 651.20 wm^-2 and the albedo of the area was low, with values ranging from 0.0028 to a value of 0.29 which is an indication of low reflectivity. This implied that more radiation was absorbed in the study area which impacted the soil temperature thereby influencing reduced soil moisture and a higher rate of evapotranspiration from plants within the study area.

Keywords: thermal energy, atmospheric transmissivity, spatial analysis, surface albedo